1. Field of the Invention
The present invention relates to a method for joining ceramic members with small electric conductivity using induction heating of the butting parts, and an insertion member to be employed in the joining method.
2. Description of the Prior Art
When ceramic members are to be jointed with each other or a ceramic member is to be jointed with a metallic member through induction heating, e.g., high frequency heating, a suitable joining agent is intervened between the members, and electricity is supplied to an induction heating coil cylindrically wound in the outer periphery of the butted portion of the members. In this case, if the ceramic members or metallic member have large electric conductivity, an induction current naturally flows in the ceramic members or metallic member, thereby heating the butted portion and joining the ceramics. On the other hand, when the ceramic members or metallic member become electrically conductive at high temperatures, after the surface of the butted portion of the members is coated with a conductive material such as metal or the like, this coating is heated with an induction current. The induction current comes to flow in the ceramic members the conductivity of which is enhanced through induction heating. In consequence, the butted portion is heated and the ceramic members are bonded. The joining method of the ceramic members as above is proposed in Japanese Patent Laid-open Tokkaisho 61-36180. Meanwhile, when insulating ceramic members are to be jointed with each other, it may be possible to insert a conductive joining agent between the members and heat the joining agent with an induction current.
The prior art of these kinds is, however, not applicable to joining of ceramic members such as Si.sub.3 N.sub.4, Al.sub.2 O.sub.3, etc. with use of an insulating joining agent which are insulating at high temperatures. Moreover, when the ceramic members having conductive properties at high temperatures, e.g., ZrO.sub.2 or the like, are to be jointed with each other or when a conductive joining agent is used for bonding, although coating of the conductive material is considered, it is difficult to effectively heat the members to high temperatures since the coating is generally considerably thinner in comparison with the members to be jointed of a huge volume. In other words, it takes a long joining time and requires a large quantity of electricity in the prior art. Further, joining is restricted only to small-size members.